iHeartRadio is Good based on the quantity of ClearChannel stations supported/available. I finally get to listen to WMMS (...and punt!) while on the road.

Pandora is Excellent (if supported) due to the Music Genome and the index of music. They even accept directly submitted music for inclusion, so the indy music is fresh and always growing. Battery life running Pandora is better than most of the other apps.

Slacker is Good. The UI is very good, the caching (if you can get it to work) is a great feature. The music index is sub-par. An index based primarily on Genre, title, album artist and year, is not going to cut it. Perhaps they can tell me why I continue to get Christmas music on my Kings of Leon station!

Nobex Radio Companion is Good. The station list is average, but the ability to send the song info and view lyrics (newest version) is something other apps lack.

Moodio.fm is Poor. The UI (or lack of), battery life, and the simple act of adding stations is old news and leaves a lot to be desired. Now that the other apps mentioned above are available, this app needs an overhaul.